Outgrowth of undesired micoorganisms in food products can be counteracted by different ways. Beside physical and chemical treatments, biological treatments such as fermentations by naturally resident and/or artificial (“starter”) microorganisms are widely used. They can change the food conditions in which growth of undesireable organisms is less favourable or completely inhibited as is the case in wine, beer, cheese or yoghourt (Holzapfel et al. 1995; Vogel, 1996). Another system of biologically induced food preservation is the supplementation of “protective cultures” acting as “biopreservatives”. Such cultures are thought    a) either to grow and competitively supress undesired organisms    b) or to grow and produce antimicrobial and antifungal agents (e.g. bacteriocins, organic acids, diacetyl, unknown metabolites)    c) or to interact by unknown mechanisms with food spoiling microorganisms.Since protective cultures generally do not participate in specific food modification processes as starter cultures, their application can also be extended to nonfood materials.
Antimicrobial activities of propionibacteria and lactic acid bacteria make them appropriate for industrial application as biopreservatives. Bio Profit (Valio Ltd., Helsinki, Finland; Wiesby GmbH & Co., Niebüll, Germany), is a commercially available co-culture of Lactobacillus rhamnosus LC705 (DSM 7061) (former Lactobacillus casei subsp. rhamnosus) and Propionibacterium freuden-reichii subsp. shermanii JS (DSM 7067), that is suggested for a controlling of yeasts and moulds (Soumalainen and Mäyrä-Mäkinen, 1999) Both organisms had been cultured together and were supposed to be used as a cell containing fermentation broth inhibiting the growth of moulds and yeasts in food. Strain Lactobacillus rhamnosus LC705 was protected in 1993 by a European patent (EP 0 576 780) to be used as a single strain or in combination with a bacterium of the genus Propionibacterium or another strain of the bacterial species Lactobacillus casei. A second, German patent (DE 199 17 715) describes protective cultures consisting of lactic acid bacteria and inhibiting the growth of toxigenic bacteria at temperatures over 7-8° C. The cultures are suggested for a preservation of food and animal food (feeding stuff) showing only a short shelf-life below 7-8° C. As soon as the storage temperature increases, the cultures promise to inhibit the growth of spoilage bacteria. In contrast, Microgard™ (Wesman Foods, Inc., Beaverton, Oreg., USA) is a commercially available milk product fermented by a P. freuden-reichii ssp. shermanii strain, followed by a pasteurisation process. The product promises effectiveness in inhibiting selected food spoilage organisms as well as pathogenic microorganisms known to cause foodborne illnesses (Daeschel, 1989; Al-Zoreky et al., 1991). Microgard™ is approved by the US Food and Drug Administration.